Polyacetylene Glycosides: Isolation, Biological Activities and Synthesis.

Polyacetylene glycosides (PAGs) constitute a relatively small class of secondary metabolites characterized by the presence of a sugar unit anomerically connected to a polyacetylene. These compounds are found in fungi, seaweed, and more often in plants. PAGs exhibit a wide range of biological and pharmacological activities and, as a result, the literature of these compounds has grown exponentially in recent years.

Unusual Application for Phosphonium Salts and Phosphoranes: Synthesis of Chalcogenides.

A novel strategy for the synthesis of sulfides and selenides from phosphonium salts and thio- or selenesulfonates, commercially available compounds, is described. When phosphoranes were used in the reaction, different products were obtained. The methodology does not require the use of metals, reactive species, or anhydrous conditions to be performed.

Efficient method for propargylation of aldehydes promoted by allenylboron compounds under microwave irradiation.

The propargylation of aldehydes promoted by microwave irradiation using allenylboron compounds in a chemo- and regioselective way is described. The corresponding products were obtained in short reaction time, high yield and purity without the need of any solvent when allenylboronic acid pinacol ester was used, or using a minimal amount of acetone when potassium allenyltrifluoroborate was used.

Structure-based design, synthesis and antitumoral evaluation of enulosides.

Enulosides, carbohydrate derivatives containing an α,ß-unsaturated carbonyl unit, were designed and obtained in high yields and isomeric purity. All synthesized compounds exhibited antitumoral activity in micromolar range against four tested tumor cells lines, being the best results observed for HL-60 cells. These compounds open new possibilities to prepare an array of more active, site-specific or selective antitumor agents. 2016 Elsevier Ltd. All rights reserved.

A Green Approach for Allylations of Aldehydes and Ketones: Combining Allylborate, Mechanochemistry and Lanthanide Catalyst.

Secondary and tertiary alcohols synthesized via allylation of aldehydes and ketones are important compounds in bioactive natural products and industry, including pharmaceuticals. Development of a mechanochemical method using potassium allyltrifluoroborate salt and water, to successfully perform the allylation of aromatic and aliphatic carbonyl compounds is reported for the first time. By controlling the grinding parameters, the methodology can be selective, namely, very efficient for aldehydes and ineffective for ketones, but by employing lanthanide catalysts, the reactions with ketones can become practically quantitative. The catalyzed reactions can also be performed under mild aqueous stirring conditions. Considering the allylation agent and its by-products, aqueous media, energy efficiency and use of catalyst, the methodology meets most of the green chemistry principles.

Stereoselective synthesis and antitumoral activity of Z-enyne pseudoglycosides.

An efficient approach for the synthesis of Z-1,3-enynes based on the coupling reaction of Z-vinyl tellurides and alkynes containing a pseudoglycoside moiety is described. The products were obtained in good yields via a stereoselective way. Preliminary screening against three tumor cell lines indicated that the synthesized compounds are promising intermediates for the synthesis of an array of more potent target structures.

Effects of α,ß-unsaturated lactones on larval survival and gut trypsin as well as oviposition response of Aedes aegypti.

Lactones are organic cyclic esters that have been described as larvicides against Aedes aegypti and as components of oviposition pheromone of Culex quinquefasciatus. This work describes the effect of six α,ß-unsaturated lactones (5a-5f) on survival of A. aegypti fourth instar larvae (L4). It is also reported the effects of the lactones on L4 gut trypsin activity and oviposition behavior of A. aegypti females. Five lactones were able to kill L4 being the lactones 5a (LC50 of 39.05 ppm), 5e (LC50 of 36.30 ppm) and 5f (LC50 of 40.46 ppm) the most promising larvicides. Only the lactone 5a inhibited L4 gut trypsin activity, with an IC50 of 115.15 µg/mL. Lactones 5a, 5c, 5d and 5e did not exert deterrent or stimulatory effects on oviposition, whereas lactone 5b exhibited a strong deterrent oviposition activity. In conclusion, this work introduces new α,ß-unsaturated lactones as promising alternatives to control A. aegypti dissemination. The larvicidal mechanism of the lactone 5a can involve the disruption of proteolysis at larval gut.

Metal free synthesis of homoallylic alcohols promoted by ultrasound.

The use of ultrasound irradiation to promote the allylation of aldehydes containing different functionalities with potassium allyltrifluoroborates is described. The method features the use of a minimum amount of acetone as solvent, without any other catalyst or promoter. The products were obtained in high yields, short reaction times, at room temperature and without the need of further purification.

Synthesis and evaluation of (-)-Massoialactone and analogues as potential anticancer and anti-inflammatory agents.

(-)-Massoialactone, an α,ß-unsaturated δ-lactone isolated from Cryptocarya massoia, and five analogues were synthesized and their antiproliferative and anti-inflammatory activities were evaluated. The lactones were able to mimic the "core" functional group required for the biological activity of their parent natural compounds suggesting that substantially altered analogues may retain their properties.

Allylation of functionalized aldehydes by potassium allyltrifluoroborate catalyzed by 18-crown-6 in aqueous media.

An efficient method for the allylation of aldehydes containing a broad range of functional groups using potassium allyltrifluoroborate is described. The reaction utilizes a catalytic amount of 18-C-6 in biphasic media under open atmosphere and room temperature to provide the corresponding homoallylic alcohols in high yields and without the necessity of any subsequent purification.

Differentiation and assignment of vinyl telluride regioisomers by (1) H-(125) Te gHMBC.

Complete (1) H, (13) C, and (125) Te NMR spectral data for some vinyl tellurides are described. The (1) H-(125) Te gHMBC experiment was used for the complete chemical shift assignment and structure elucidation of a mixture of regioisomers. The assignment ((125) Te NMR) and coupling constants (J(H,H) ) for all regioisomers are described for the first time.

Regioselective synthesis of isochromenones by iron(III)/PhSeSePh-mediated cyclization of 2-alkynylaryl esters.

A series of 4-Se-(Te, S)-isochromenones and 3-substituted isochromenones were synthesized in good yields via FeCl(3)-mediated cyclization of alkynylaryl esters with different diorganyl dichalcogenides. This methodology was carried out at room temperature, using inexpensive and environmentally friendly iron salts as metallic source and under air atmosphere. The reaction showed to be tolerant to a range of substituents bonded into the aromatic ring of the diorganyl dichalcogenides as well as to alkyl groups directly bonded to the chalcogen atom. Alternatively, the cyclization reaction of 2-alkynylaryl esters with FeCl(3), in the absence of diorganyl dichalcogenide, gave the isochromenones without the chalcogen moiety in the structure. This approach proved to be highly regioselective, providing only six-membered ring products, once the possible five-membered products were not observed in any experiments.

Selective base-promoted synthesis of substituted selenophenes by carbocyclization of (Z)-benzylselenoenynes.

We herein described the synthesis of several 3-benzyl-2,5-diarylselenophene derivatives in moderate to good yields using (Z)-benzylselenoenynes as starting material in carbocyclization reactions. The reactions were carried out under mild conditions using only t-BuOK as base, in the complete absence of transition metals or additives. The cyclized 3-benzyl-2,5-diarylselenophenes obtained in the current protocol appear highly promising and attractive intermediates for the synthesis of polysubstituted selenophenes. For instance, 3-benzyl-2,5-diphenylselenophene was treated with Br(2) provided the corresponding 3-benzyl-4-bromo-2,5-diphenylselenophene in high yield. 4-Bromoselenophene derivative was applied as substrate in the palladium catalyzed cross-coupling reactions with boronic acids to give the Suzuki type products in excellent yields.

Synthesis of 2,3-dihydroselenophene and selenophene derivatives by electrophilic cyclization of homopropargyl selenides.

The synthesis of several highly functionalized 2,3-dihydroselenophenes from homopropargyl selenides via electrophilic cyclization is described. Electrophiles such as I(2), ICl, and PhSeBr were used in a simple process employing CH(2)Cl(2) as solvent at room temperature, which gave the cyclized products in high yields. 4-Iodo-2,3-dihydroselenophenes obtained by this methodology were submitted to a dehydrogenation reaction using 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) to give 3-iodoselenophenes. 4-Iodo-5-phenyl-2,3-dihydroselenophene was also submitted to the thiol copper-catalyzed and Heck-type reactions giving the desired products under mild reaction conditions.

(1)H, (13)C, (19)F and (11)B NMR spectral reference data of some potassium organotrifluoroborates.

Complete (1)H, (13)C, (19)F and (11)B NMR spectral data for 28 potassium organotrifluoroborates are described. The resonance for the carbon bearing the boron atom is described for most of the studied compounds. A modified (11)B NMR pulse sequence was used and better resolution was observed allowing the observation of (11)B-(19)F coupling constants for some of the studied compounds.

Toxicological investigation and antinociceptive property of potassium thiophene-3-trifluoroborate.

The aim of the present study was to evaluate pharmacological and toxicological properties of potassium thiophene-3-trifluoroborate (RBF(3)K). The acute effect of RBF(3)K was evaluated on mice. To this end, mice received a single dose of RBF(3)K (25, 50, and 100 mg/kg, by oral route, p.o.) and after 72 hrs, blood, liver, and kidney samples were collected. delta-Aminolevulinate dehydratase, catalase and glutathione-S-transferase activities, thiobarbituric acid-reactive substances and vitamin C levels, as well as plasma aspartate and alanine aminotransferase activities and creatinine levels were determined. Hepatic and renal lipid peroxidation levels in treated mice did not differ from those in control mice. No significant differences between treated and control mice were detected in hepatic and renal delta-aminolevulinate dehydratase activity. Aspartate and alanine aminotransferase activities as well as urea and creatinine levels were similar among the groups. In contrast, results obtained from in vivo experiments revealed that RBF(3)K, orally administered, reduced peritoneovisceral pain induced by acetic acid administered i.p. Doses of 1, 5, 10, 25, 50, and 100 mg/kg of RBF(3)K were assessed in the antinociceptive investigation and the effect was significantly different than control groups from 5 mg/kg. It was observed that alpha(2-)adrenergic and serotonergic, but not opioidergic, receptors appear to be involved in orally administered RBF(3)K. Mice treated with RBF(3)K did not reveal any motor impairment in the open field. This is a promising compound for more detailed pharmacological studies involving organotrifluoroborate compounds.

Electrophilic cyclization of 2-chalcogenealkynylanisoles: versatile access to 2-chalcogen-benzo[b]furans.

An efficient synthesis of 2-chalcogen-3-substituted-benzo[b]furan compounds has been accomplished via electrophilic cyclization reaction of 2-chalcogenealkynyl anisoles using I(2), ICl, Br(2), and PhSeBr as electrophile sources. The product distributions were strongly dependent on the nature of substituents in the aromatic ring of anisole and on the chalcogen atom directly bonded to the triple bond. The 2-chalcogen-3-iodo-benzo[b]furans obtained smoothly underwent conversion to more complex structures of benzo[b]furan derivatives via palladium- or copper-catalyzed cross-coupling reaction with thiols, diphenyl diselenides, and zincates.

Eu(III) dithiocarbamate complex and N-p-tolylsulfonylphenylalanine as a novel chiral catalyst for the asymmetric synthesis of cyanohydrins.

The use of a new chiral lanthanide complex derived from a europium dithiocarbamate complex and a N-tosylated amino acid for the asymmetric synthesis of cyanohydrins is described. In some cases, high enantioselectivities were observed.

Hydroselenation of alkynes by lithium butylselenolate: an approach in the synthesis of vinylic selenides.

Vinylic selenides were prepared in good yields by hydroselenation of alkynes with lithium butylselenolate generated by reaction of n-butyllithium with elemental selenium. The regio- and stereochemistry of the hydroselenation depend on the nature of the substituents bonded to the alkyne.

Efficient chiral discrimination by 77Se NMR.

[reaction: see text] Several (77)Se NMR experiments were performed by titrating a sample of selenides with the chiral shift reagent methylbenzylamine (MBA), followed by acquisition of (77)Se NMR spectra. Eventually, we observed the appearance of two anisochronous resonances, with a relatively large separation, from 37 to 56 Hz, corresponding to the formation of the diastereomeric complexes. This methodology avoids derivatization processes, and the studied compound can be easily recovered from the NMR tube.